Document WO2008015044, which is incorporated by reference, provides a rotation rate sensor which consists of two nested seismic elements which are coupled to one another via springs. Both elements have the same masses. In the drive mode, both masses oscillate in antiphase in the x direction. The read mode is characterized by antiphase oscillation of the seismic masses away from the substrate plane in the z direction, thus allowing rotation rates about the x axis to be detected. Because of the mass equilibrium and because of the fact that their centers of gravity lie on one another, neither mode can be excited directly by linear or rotational disturbances. Nevertheless, those mode forms in which both masses oscillate in the same phase on or away from the plane also exist. These in-phase modes can easily be excited directly by linear vibration, and this adversely affects the operation of the rotation rate sensor. The spring concept leads merely to a mode separation and not to suppression of the in-phase modes. In particular, seismic elements means seismic masses.
The sensor from the document US2004/0154398, which is incorporated by reference, is designed in a similar manner with the read direction lying in the y direction, thus allowing rotation rates about the z axis to be measured. In this case as well, the rotation rate sensor consists of two nested seismic elements, which are coupled to one another via springs. Both elements have the same masses. In the drive mode, both masses oscillate in antiphase in the x direction. The read mode is characterized by antiphase oscillation of the seismic masses in the y direction, thus allowing rotation rates about the z axis to be detected. Because of the mass equilibrium and because of the fact that their centers of gravity lie on one another, neither mode can be excited directly either by linear or by rotational disturbances. Nevertheless, those mode forms in which both masses oscillate in phase in the x and/or y directions also exist. These in-phase modes can easily be excited directly by linear vibration, and this adversely affects the operation of the rotation rate sensor. The spring concept leads merely to a mode separation and not to suppression of the in-phase modes.
Documents WO2004097432, WO2008021534, DE102006052522, DE102005051048, U.S. Pat. No. 6,892,575, EP1832841, WO2008051677, which are incorporated by reference, describe sensors which simultaneously measure rotational movements about the x and y axes—that is to say they cannot measure rotational movements at right angles to the wafer plane. The sensor principles mentioned are single-chip solutions; that is to say the sensor elements for measurement of the orthogonal rotation rates are located on the same monolithic silicon chip. Furthermore, they have the common feature that only a single primary movement is excited for both sensitive axes. This saves control-system complexity; furthermore, the chip area is smaller than in the case of two separate sensors. When a Coriolis force is excited by rotational movement about the x and/or y axes, oscillations are excited with movement components in the z direction. If the intention is to use these sensors to measure rotation rates about the z axis, the sensors must be installed by means of construction and connection technology, that is to say they must be mounted through an angle of 90° with respect to the planar preferred direction—the wafer plane. This leads to additional costs.
Patent specification EP 1918723 B1, which is incorporated by reference, provides a gyroscope which can simultaneously measure rotational movements about the x and z axes. This is once again a single-chip solution with a single primary mode. However, this sensor has the disadvantage that the two read modes—also referred to as the secondary mode (detection of the rotation about the z axis) and tertiary mode (detection of the rotation about the x axis)—can be excited directly by rotational movements, which leads to the sensor being sensitive to disturbances caused by environmental influences.
Document WO9817973A1, which is incorporated by reference, provides a three-axis gyroscope. In this case, in the drive mode, four masses which are each offset through 90° oscillate in the radial direction. This arrangement can distinguish between Coriolis forces in all three spatial directions. However, the individual masses are not directly connected to one another as a result of which linear accelerations at right angles to the substrate plane, for example, lead to the individual masses being deflected away from the substrate plane.